1. Field of the Invention
The present invention relates to a fiber-optic sensor assembly and a method for sensing force and displacement.
2. Description of the Prior Art
There have been various attempts to create a durable, inexpensive, fiber-optic force and displacement sensor. One such sensor is known as the Fiber Bragg grating sensor (FBG) that utilizes various changes in the refractive index of a fiber core in a fiber-optic cable to measure force and pressure. However, the FBG and other similar sensors that use alternating layers with different refractive indexes suffer from common drawbacks such as weak and brittle axial tensile strength and temperature dependency. Another such sensor is disclosed in U.S. Pat. No. 8,879,067 (hereinafter the '067 Patent) that utilizes a wavelength dependent sensor that reflects or transmits a wavelength-specific spectral feature. The '067 Patent discloses using a laser light source to produce a plurality of single wavelength light beams in electromagnetic communication with a two-way fiber-optic cable. The two-way fiber-optic cable extends to a distal end for discharging the combination light beam. A collimating lens is spaced from the distal end at a first distance. A wavelength sensitive element is spaced from the collimating lens a second distance. The '067 Patent assembly is wavelength dependent and thus measures displacement as a function of the change of wavelength. With advances in technology, there exists an opportunity to create a sensor that is intensity dependent and not wavelength dependent.